Liquid crystal display devices with a huge screen have been used as display devices for amusement facilities, information displays, digital signages and so on. While these applications are expanding, some people attempt to realize a pseudo-display device with a huge display screen by assembling a number of liquid crystal display devices densely together with no gaps left between them (which will be sometimes hereinafter referred to as a “tiling technique”). Such an arrangement is sometimes called a “multi-display system” (or a “multi-screen system”) and has attracted a lot of attention these days as a scheme for providing a high-definition huge screen.
In such a multi-display system, however, the seam between adjacent display devices is often easily sensible to the viewer's eye, which is a problem. Now it will be described how and why such a problem arises in a liquid crystal display device, for example.
A liquid crystal display device includes an liquid crystal panel, a backlight unit, circuits and power supplies for supplying various kinds of electrical signals to the liquid crystal panel, and a housing or bezel (such as a rim member or a frame member) to house all of these components.
The liquid crystal panel includes a display area in which a plurality of pixels are arranged and a frame area which surrounds the display area. In the display area (active area), pixel electrodes, TFTs and other members are arranged and an image or video is displayed. In the frame area, on the other hand, arranged are a seal member to seal a liquid crystal material between the substrates, wiring connected to scan lines and signal lines, and terminals to be connected to an external driver circuit. In addition, to prevent the display quality from being debased on the periphery of the display area, an opaque member is often provided in the frame area.
The frame area is an area that does not contribute to a display operation (i.e., a non-display area), and therefore, is sensed to the viewer's eyes as a non-display area (black frame) representing the seams of the display device. If the frame area can be narrowed, then the seams will be less sensible to the eye. However, even though the frame area of display devices has been narrowed year after year, it is impossible in principle to eliminate the frame area altogether.
Methods for making those seams less sensible to the eye in display devices which form a multi-display system have been studied in the related art. For example, Patent Documents Nos. 1 and 2 disclose a technique for making the seams less sensible to the eye by providing a light-transmitting cover for each display panel so that the cover is located closer to the viewer than the display panel is.
The end portion of the light-transmitting cover disclosed in Patent Documents Nos. 1 and 2 includes a curved portion which functions as a lens. That curved portion (lens portion) of the light-transmitting cover is typically arranged to cover not only the frame area of the display panel but also a part of the display area near the frame area (which will be sometimes hereinafter referred to as a “peripheral display area”). Part of the light that has gone obliquely out of pixels that are arranged in the peripheral display area (which will be hereinafter referred to as “peripheral pixels”) is incident on the light-transmitting cover and then refracted by the lens portion toward the frontend of the panel. As a result, it looks to the viewer's eye as if an image was being displayed on the frame area, too, thus providing an image, of which the seams are less sensible to the viewer's eye.
It should be noted that such a problem of easily sensible seams (or the problem that the frame area cannot be narrowed beyond a certain limit) arises in not only liquid crystal display devices but also whenever a number of direct-viewing display devices, including PDP (plasma display panels) organic EL display devices, and electrophoretic display devices, are tiled together. In any case, the seams can be made less sensible to the eye by using a light-transmitting cover with a lens described above.
On top of that, not just display devices for use to make up a multi-display system but also a display device to be used by itself are required to narrow their frame area as much as possible. That is why it is advantageous to use such a light-transmitting cover with a lens, because an image can also be displayed in the frame area in that case.